The need for a high performance and reliable energy source is well understood. Lithium batteries represent a very attractive solution to these energy needs due to their superior energy density and high performances. Lithium batteries having solid electrolytes offer significant advantages over other lithium battery families because of the elimination of fear of electrolyte instability and combustion, a wider operating temperature range, and relative ease of miniaturization. The solid electrolyte is generally applied in thin film form to minimize losses in the electrolyte. Currently, the most widespread solid lithium electrolyte is Li3.3PO3.9N0.17 (LiPON). However, LiPON electrolytes are sensitive to moisture and oxygen in ambient air and as such limits their applicability.
Lithium lanthanum titanate (LLTO) has been identified as an attractive alternative to LiPON electrolytes. Currently, the La0.5Li0.5TiO3 form of LLTO and its cation deficient modifications have been found to have high lithium ion conductivity. Despite all crystalline LLTO modifications having high conductivity, they turn out to be unstable for lithium solid film battery applications because they are unstable in contact with lithium metal anodes. This instability manifests itself in the crystalline LLTO electrolytes becoming an electronic conductor when in contact with lithium metal due to Li+ ion insertion into the LLTO electrolyte. This effect is facilitated by the presence of spatially extended electronic states in the crystalline LLTO electrolyte. Amorphous versions of LLTO electrolytes typically do not exhibit the electronic conduction instability of the crystalline LLTO electrolytes while maintaining the high lithium ion conductivity of its crystalline counterpart.
Amorphous LLTO electrolyte thin films have been prepared using pulsed laser deposition (PLD) techniques from crystalline targets. Measured lithium conductivities of these amorphous LLTO electrolyte samples are at least an order of magnitude higher than LiPON electrolytes conductivity and range for 1E-5 to 1E-3 S/cm−1 Stability of the amorphous LLTO electrolyte was successfully demonstrated by fabricating a solid lithium ion battery that used amorphous LLTO as its electrolyte, lithium metal as its anode and LiCoO2 as its cathode. This battery was successfully cycled between 4.3 and 3.3V at room temperature. While amorphous LLTO electrolytes show excellent promise as a lithium battery solid electrolyte candidate material, its pulse laser deposition technique method of preparation is not convenient for large scale manufacturing purposes.
It would be beneficial to provide an amorphous LLTO material which may be suitable for use in batteries, or other electrochemical devices or lithium ion conductive systems. Accordingly, it is to the provision of such that the present invention is primarily directed.